Some Cells Refuse References and Won't Populate Referenced Data

Okay, after a few years using Numbers this is a new one on me!

Two tabs, each with a table.

One is the master and the second tab and table is the replication where I use = and then go to the master tab and table click on a cell I want to replicate in the copy tab / table.

Everything was fine until I got to J4 where a blue 0 appeared... I tried dragging the I4 cell data over to see if it would populate the "37d 23h" into it but still a blue 0? So I deleted the contents of the cell with its blue 0 and tried again. Blue 0... Deleted the column, nope.... Nothing but blue 0's?

The blue table is the master tab / table and the green tab / table is what I am using to mirror the contents of the blue table into the green table. Plea ignore the black font or blue font cell highlighting rules.

Thanks in advance for any help.

[Edited by Moderator]